For example, in a mobile communication terminal, a plurality of band pass filters are used in response to various communication methods. For example, there are a FDD (Frequency Division Duplex) method and a TDD (Time Division Duplex) method as a communication method that transmits a transmission signal to a single antenna and receives a reception signal from the single antenna.
For example, in the FDD method, a transmission band differs from a reception band, as described in Japanese Laid-open Patent Publication No. 09-98046 (“Patent Document 1”). Therefore, a demultiplexer equipped with a transmission filter that sets the transmission band as a pass band and a reception filter that sets the reception band as a pass band is used. In this demultiplexer, a transmission signal is transmitted from an antenna via the transmission filter, but does not pass the reception filter. On the contrary, a reception signal which the antenna receives passes the reception filter, but does not pass the transmission filter. Thereby, the transmission of the transmission signal and the reception of the reception signal are enabled with the single antenna.
For example, in the TDD method, the transmission band and the reception band overlap with each other, as described in Japanese Laid-open Patent Publication No. 2010-56876 (“Patent Document2”). Therefore, a period in which the transmission signal is transmitted and a period in which the reception signal is received are divided by switching a switch or the like. Thereby, the transmission of the transmission signal and the reception of the reception signal are enabled with a single antenna. A technique in which a plurality of antennas are provided in a mobile communication terminal is described in Japanese Laid-open Patent Publication No. 2011-254451 (“Patent Document 3”).
It is demanded to perform simultaneously the transmission and reception of different communication methods. For example, it is demanded to perform simultaneously the transmission and reception using the FDD method and the transmission and reception using the TDD method. By performing simultaneously the transmission and reception of the different communication methods, data communication and voice communication can be achieved simultaneously by using the different communication methods.